A component mounting line which produces a mounting substrate on which electronic components are mounted includes a plurality of kinds of component mounting devices such as a component mounting device which mounts the electronic components on the substrate. In these component mounting devices, a substrate conveyance mechanism is provided which conveys the substrate as an object of an operation by a transport conveyor from an upstream side device and positions and holds the substrate in a prescribed working position for mounting. As such a substrate conveyance mechanism, there is known a substrate conveyance mechanism having a structure that the transport conveyor is divided into a stand-by area where the substrate carried in from the upstream side waits and a working area where a prescribed mounting operation is performed in order to eliminate a waste waiting time in a conveyance of the substrate to the utmost and improve a productivity (see PTL 1, for instance). In the related art disclosed in an example of the patent literature, three conveyor mechanisms which are respectively individually driven are arranged in series, so that a carrying-in operation and a carrying-out operation of the substrate can be performed irrespective of a state of the substrate.